Heretofore, in known practices, it has been customary in overlock sewing machines and the like to mount a needle in a needle bar when the needle bar is raised to a position near the "top dead center." However, in such cases, both the upper knife and the looper are projected upwardly with respect to the throat plate and are thus located adjacent the needle, causing interference with the bar. Thus, much difficulty has been encountered in mounting the needle to the needle bar. Moreover, when a two needle overlocking sewing machine is used, it is even more troublesome to mount the needle to the needle bar.
In order to avoid these problems, a device has previously been proposed for use in mounting the needle. FIGS. 3 to 5 illustrate such a conventional needle mounting device which was intended to avoid the earlier manual needle mounting operations, which relied on an operator's fingers to mount the needles.
In the drawings of FIGS. 3-5, numeral 1 denotes a needle mounting device which includes a needle holder 2 for holding a sewing machine needle 4. The needle 4 is formed at its front face with a thread guide 4c axially extending along the needle. A nipper 3 is provided including a branch 3c formed into fork end 3a, 3b between which the needle holder 2 is releasably mounted.
As shown in FIG. 5, the needle holder 2, which is formed of flexible materials such as rubber, synthetic resin, cork or the like, is shaped into a plate form of substantially oval cross section. The needle holder 2 is provided, at its opposite sides, with a flat surface 2a and a deformed arcuated surface 2b so as to primarily determine the mounting orientation of the needle holder 2 with respect to the nipper 3. This configuration is intended to prevent the needle holder 2 from being mounted in an improper orientation.
As shown in FIGS. 4 and 5, the needle holder 2 is formed with a directional line 5. A guide line 6 intersects the directional line 5 at a right angle on the upper surface of the needle holder. At the intersecting point of the two lines 5, 6, a hole 7 is bored through the needle holder 2 in the direction of the plate thickness. The hole 7 is adapted to releasably receive (by pressure) and to hold the needle 4 after aligning the thread guide 4c with the directional line 5.
FIG. 3 also illustrates a needle bar 8 with a needle accommodating channel 9 and a needle set screw 10 for locking the needle 4 after it is inserted in the needle accommodating channel 9.
For mounting the needle in the needle bar 8, the needle 4 is initially forced from above into the through hole 7 of the holder 2 with the thread guide 4c aligned with the directional line 5. The needle 4 is thus held in position within the holder 2. Then, the butt or tail end of the nipper 3 is clamped to tightly hold the needle 4 through the holder 2 The needle holder 2, supported by the nipper 3, is moved so as to have access to the needle bar 8. The needle shank is urged against and into the inside of the needle accommodating channel 9 of the needle bar 8 for locating the needle 4 in its correct position and may be rotated about its axis inside the needle accommodating channel 9 for position alignment.
The set screw 10 is then secured to lock the needle 4 in its correct position. The mounting device 1 is then downwardly moved to draw the needle 4 out of the hole 7.
Although useful, the aforementioned conventional needle mounting device has several disadvantages.
First, in the conventional device, it is necessary to have the thread guide aligned with the directional line 5 and then to force the needle into the through hole in the needle holder 2 for mounting the needle thereto. This requires a complicated operation. Further, the operator may inadvertently force the needle into the through hole in misalignment therewith, resulting in damage to the thread guide and in difficulty in drawing the needle out of the through hole.
Furthermore, once the needle has been forced into the through hole, it may be difficult to remove the needle mounting device from the needle after mounting the needle to the needle bar. The needle may be thereby damaged unless careful attention is paid when the needle is drawn out.
Further still, if poor engagement is made between the needle and the through hole 7, the needle may be readily drawn out of the needle holder, contrary to what is intended in operation of the device, and this may result in deterioration of the workability of the device.
It is therefore an object of the invention to provide a needle mounting device for securably holding the needle, for readily mounting the needle to a needle bar and for readily disengaging the needle from the needle bar.
It is another object of the invention to provide a needle mounting device for firmly mounting the needle to the needle bar in the correct position.
It is a further object of the invention to provide a needle mounting device for receiving the needle without involving misalignment and damage to the needle.
It is another object of the invention to provide a needle mounting device which is capable of quickly, readily, and properly mounting the needle to the needle bar without requiring additional tools, thus saving labor and time.
It is a further object of the invention to provide a needle mounting device which is capable of facilitating the mounting of the needle to the needle bar through proper orientation and positional alignment of the needle with respect to the bar.
It is still further object of the invention to provide a needle mounting device which is capable of readily determining the needle orientation with respect to the device and the needle bar.
It is still further object of the invention to provide a needle mounting device for use with both industrial sewing machines and household sewing machines.